Hello Niranjan,

I just replied to Rob Sargent regarding this.  Did you see that reply?

Maybe I’m not using Glassfish correctly, but if I set the maximum pool size to 
1, the system almost immediately outputs an error message saying that it is 
unable to allocate any more connections and crashes.  That’s why I have set a 
large maximum pool size.

Dan Schwartz

From: Niranjan Rao <n...@paymentus.com>
Sent: Tuesday, August 5, 2025 12:54 PM
To: users@tomcat.apache.org
Subject: Re: [EXTERNAL EMAIL] RE: How to access a REST service

On 8/5/25 09:43, Daniel Schwartz wrote: > Well, I guess that this is a top 
post. But this message is getting > longer with all the replies. I don’t think 
it is a memory leak. I’m > fairly sure that I’m closing every connection 
immediately
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On 8/5/25 09:43, Daniel Schwartz wrote:

> Well, I guess that this is a top post. But this message is getting

> longer with all the replies. I don’t think it is a memory leak. I’m

> fairly sure that I’m closing every connection immediately after using

> it. It seems that most of my database

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> Well, I guess that this is a top post.  But this message is getting longer 
> with all the replies.

>

> I don’t think it is a memory leak.  I’m fairly sure that I’m closing every 
> connection immediately after using it.  It seems that most of my database 
> queries are coming from web crawlers, and there are a few hundred accesses 
> every day.  I was getting error messages from Glassfish saying that it 
> couldn’t allocate any more connection objects and then crashing.  At that 
> time the maximum pool size was the default, which is 32.  So I believe it was 
> just being overloaded by the web crawlers.  Now that I have increased to 
> 1000, the system has stopped crashing.

>

> But I have to admit that I really don’t understand how these connection 
> pooling systems work.  My understanding is that only as many connection 
> objects are created and placed in the pool as are needed, so even if you set 
> the upper limit high it doesn’t necessarily mean that you will have that 
> many.  Once a database session terminates, then that connection object 
> becomes available for future use.  So at any given time, the number of 
> connection objects in the pool would be the maximum number of simultaneous 
> connections that have been made so far, and not necessarily the total maximum 
> that are allowed (in my case 1000).  Is this correct?

>

> Dan Schwartz

>



The default is a reasonable number depending upon traffic. Is your site

fairly busy? We manage a fairly busy site with lot database activity and

even then we don't have to go 1000 connections which essentially might

boil down to 1000 concurrent requests. Are you really getting that many

requests simultaneously? As others have indicated there is a good chance

you have connection and/or other resource leaks in your code. There are

some debugging hints posted like setting max connections to 1 in your

dev environment and see if it works cleanly.

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